1. Field of the Invention
The present invention relates to the field of semiconductor processing equipment and, more particularly, to a technique of utilizing multivariate analysis for monitoring and controlling a plasma process.
2. Prior Art
In the fabrication and processing of semiconductor wafers, such as silicon wafers, a variety of different semiconductor equipment and/or tools are utilized. These processing tools are well known in the prior art and include photolithographic machines, etchers, deposition equipment, furnaces, as well as a variety of sensors and control equipment. Although the capabilities of these types of semiconductor processing equipment have improved over the years, the technique of monitoring the ongoing process has not necessarily kept pace with the improvements. In the field of monitoring the ongoing semiconductor process, current practices generally utilize ex-situ process monitoring. A problem with ex-situ monitoring is that the results are not available until the end of the process or if intermediate readings are required, the ongoing process must necessarily be interrupted in order to obtain the required reading.
Furthermore, where a number of parameters are monitored for a given process, it is difficult to determine the dependency of one parameter to the others. Such processing parameter correlations are difficult to obtain, but are made so much more difficult when measurements are being taken for the purpose of providing in-situ control of the ongoing process.
The present invention provides for a technique to obtain real-time, in-situ control of a plasma process and, more specifically, in the processing of semiconductor wafers.